1. Field of the Invention
The present invention relates to bisphenyl-2,3,5,6-tetrafluoro-4-trifluoromethylphenylphosphine oxide compounds and synthesis thereof, more particularly to novel bisphenyl-2,3,5,6-tetrafluoro-4-trifluoromethylphenylphosphine oxide compounds having both a perfluorinated benzene substituent and phosphine oxide moiety, which is useful as a monomer for preparing polyimides having a low dielectric constant and a superior adhesion while maintaining the superior thermal and mechanical properties of polyimides themselves, and a synthesis thereof.
2. Background
Polyimides have a wide scope of applications as materials for electronic products, molding products, heat-resistant adhesives, and insulation due to their superior insulating properties, thermal stability at high temperature, glass transition temperature, heat resistance, chemical resistance, mechanical property, etc. compared with other conventional organic polymers. Further, the superior thermal and chemical stabilities as well as low dielectric constant of the polyimides have extended their use even as a material for preparing inter-layer insulating films and protection films of semiconductor chips. However, the polyimides developed so far are still not sufficient to be used for manufacturing gigabyte (GB) level integration chips, and thus there has been an urgent need to develop polyimides with much improved processability and lower dielectric constant.
Recent studies have revealed that fluorine compounds, due to their superior processability, low hygroscopy, low dielectric constant and good chemical stability, can improve solubility, electrical insulation, and chemical resistance. This is because each fluorine atom has small van der Waals radius, highest electronegativity, large binding energy with other elements, thus reducing surface tension by decreasing intermolecular attraction. Therefore, various kinds of monomers containing fluorine compounds have been developed in order to obtain polyimides having superior processability and low dielectric constant while maintaining their superior thermal and mechanical properties. Further, fluorine-containing polyimides are widely used in high-precision electronics industries such as manufacturing high integration connecting device packages.
For polyimides to be used as electronics materials, especially as those for manufacturing semiconductor chips, it is essential for them to have superior adhesion in addition to superior thermal and mechanical stabilities and low dielectric constant. However, fluorine-containing polyimides in general have relatively low adhesion, and to overcome this defect, there have been developed polyimides containing phosphine oxide, which are known effective in improving adhesion and flame retardancy, in addition to fluorine. Bis(3-aminophenyl)phenylphosphine oxide (DAPPO) developed by Professor J. E. McGrath and his colleagues of Virginia Tech., U.S. is a good example [M. F. Martinez-Nuez et al., Polymer Preprint, 35, p. 709 (1994)].
As stated above, polyimides, which have superior thermal stability and superior mechanical and electrical properties, should also have sufficient adhesion and low dielectric constant to be used as materials for manufacturing high integration electronics devices with multi-layered structures. Therefore, there has been a long-felt need for the development of monomers for efficiently synthesizing such polyimides.